语法解读

　　本单元的语法项目是主语从句的用法,下面我们来总结一下。

　　主语从句的两种结构和三类引导词：

　　英语中的主语从句(the subject clause）在句中作主语,有以下两种结构：

　　1）主语从句位于句首。如：

　　What he wanted to see was an end to all the armies of the world.

　　他想要看到的是世界军备竞赛的结束。

　　2）主语从句位于句尾,使用先行词it作形式主语。如：

　　It was right that the temple was rescued.这座庙被拯救了,这很好。

　　在下列情况下,一般使用形式主语it,而将真正的主语从句放在句尾,谓语是seem,appear,be(im）possible,be a pity,be a wonder,be likely等。如：

　　It appeared to scientists on earth that the stars had moved.

　　在地球上的科学家看来,这些星体已经移动了。

　　在It is known...;It is said...;It is hoped...;It is believed...等惯用的被动结构中。如：

　　It is believed that before writing was developed,people in China used to keep records by putting a number of stones together.

　　据信,在文字发明之前,中国人靠把许多石头聚集在一起来做记录。

需要注意的是：当主语从句放在句尾而用形式主语时,形式主